Don't emit layerModified for every atomic change made during a bulk

operation to the vector layer edit buffer Eg Instead of emitting layerModified for every individual feature in a call to QgsVectorLayer::addFeatures, we defer the signal and emit it only once after adding all the features. This avoids a lot of expensive, unnecessary work which is triggered by the signal
qgis · Nov 18, 2022 · ecfa173 · ecfa173
1 parent 332a3fd
commit ecfa173
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Showing 3 changed files with 32 additions and 3 deletions.
diff --git a/python/core/auto_generated/vector/qgsvectorlayereditbuffer.sip.in b/python/core/auto_generated/vector/qgsvectorlayereditbuffer.sip.in
@@ -331,6 +331,7 @@ Updates an index in an attribute map to a new value (for updates of changed attr
 
 
 
+
 };
 
 /************************************************************************

diff --git a/src/core/vector/qgsvectorlayereditbuffer.cpp b/src/core/vector/qgsvectorlayereditbuffer.cpp
@@ -53,6 +53,9 @@ bool QgsVectorLayerEditBuffer::isModified() const
 
 void QgsVectorLayerEditBuffer::undoIndexChanged( int index )
 {
+  if ( mBlockModifiedSignals )
+    return;
+
   QgsDebugMsgLevel( QStringLiteral( "undo index changed %1" ).arg( index ), 4 );
   Q_UNUSED( index )
   emit layerModified();
@@ -149,12 +152,23 @@ bool QgsVectorLayerEditBuffer::addFeatures( QgsFeatureList &features )
   if ( !( L->dataProvider()->capabilities() & QgsVectorDataProvider::AddFeatures ) )
     return false;
 
+  // we don't want to emit layerModified for every added feature, rather just once for the batch lot
+  mBlockModifiedSignals++;
+
   bool result = true;
+  bool anyAdded = false;
   for ( QgsFeatureList::iterator iter = features.begin(); iter != features.end(); ++iter )
   {
-    result = result && addFeature( *iter );
+    const bool thisFeatureResult = addFeature( *iter );
+    result = result && thisFeatureResult;
+    anyAdded |= thisFeatureResult;
   }
 
+  mBlockModifiedSignals--;
+
+  if ( anyAdded )
+    emit layerModified();
+
   L->updateExtents();
   return result;
 }
@@ -198,11 +212,16 @@ bool QgsVectorLayerEditBuffer::deleteFeatures( const QgsFeatureIds &fids )
     return false;
   }
 
+  // we don't want to emit layerModified for every deleted feature, rather just once for the batch lot
+  mBlockModifiedSignals++;
+
   bool ok = true;
-  const auto constFids = fids;
-  for ( QgsFeatureId fid : constFids )
+  for ( QgsFeatureId fid : fids )
     ok = deleteFeature( fid ) && ok;
 
+  mBlockModifiedSignals--;
+  emit layerModified();
+
   return ok;
 }
 
@@ -231,6 +250,10 @@ bool QgsVectorLayerEditBuffer::changeGeometry( QgsFeatureId fid, const QgsGeomet
 bool QgsVectorLayerEditBuffer::changeAttributeValues( QgsFeatureId fid, const QgsAttributeMap &newValues, const QgsAttributeMap &oldValues )
 {
   bool success = true;
+
+  // we don't want to emit layerModified for every changed attribute, rather just once for the batch lot
+  mBlockModifiedSignals++;
+
   for ( auto it = newValues.constBegin() ; it != newValues.constEnd(); ++it )
   {
     const int field = it.key();
@@ -243,6 +266,9 @@ bool QgsVectorLayerEditBuffer::changeAttributeValues( QgsFeatureId fid, const Qg
     success &= changeAttributeValue( fid, field, newValue, oldValue );
   }
 
+  mBlockModifiedSignals--;
+  emit layerModified();
+
   return success;
 }
 

diff --git a/src/core/vector/qgsvectorlayereditbuffer.h b/src/core/vector/qgsvectorlayereditbuffer.h
@@ -330,6 +330,8 @@ class CORE_EXPORT QgsVectorLayerEditBuffer : public QObject
 
     QgsVectorLayerEditBufferGroup *mEditBufferGroup = nullptr;
 
+    int mBlockModifiedSignals = 0;
+
     friend class QgsGrassProvider; //GRASS provider totally abuses the edit buffer
 
   private: